TORONTO--Residual masses are a frequent finding after treatment of Hodgkins disease. However, CT scans and MRI cannot reliably distinguish between scar tissue and viable tumor in these patients. A German study suggests that whole-body 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) may be useful in determining the viability of these masses.
"The residual masses found after treatment of Hodgkins disease can offer a problem because, if they are viable, the patient needs further treatment," Bernhard M. Dohmen, MD, said at the 45th annual meeting of the Society of Nuclear Medicine. "FDG-PET has shown to be sensitive to malignant cells in this cancer," he noted.
Dr. Dohmen and his colleagues at Eberhard-Karls-University of Tubingen studied 30 Hodgkins disease patients with 39 sites classified by CT or MRI as residual tumor (18 sites) or disease recurrence (21 sites). Patients then underwent whole-body FDG-PET. Findings were validated by histology or clinical follow-up for more than 3 months.
Results with FDG-PET
The FDG-PET scans showed 7 areas of hypermetabolic tissue; 6 of these were residual disease (see Figure 1), and the one false-positive was scar tissue from earlier irradiation of a mediastinal bulk. All of the 11 sites classified as normal (absence of viable tumor) were negative on FDG-PET scans.
FDG-PET correctly identified all 19 sites of relapsed Hodgkins disease. In addition, FDG-PET correctly classified an enlarged axillary lymph node as negative (see Figure 2).
A site of histologically nonspecific abdominal lymphadenitis showed increased FDG uptake and was falsely rated positive. Thus, overall sensitivity for FDG-PET was 100%, with specificity of 86%.
"FDG-PET appears to be suitable to classify lymphoma metastases," Dr. Dohmen said. "It has the potential to separate patients who need further therapy from those who do not. FDG-PET results might be used to help form an individualized treatment strategy for patients with difficult disease."